Sinn Fein leader Gerry Adams says he's taking his IRA-allied party into "uncharted territory" after its landmark vote in support of the Northern Ireland peace accord.

Backed by 331 of the party's 350 delegates, Adams ended Sinn Fein's traditional boycott of the Northern Ireland government - a policy as old as the party's opposition to British rule of the 77-year-old province."This was huge - a watershed," Adams said after Sunday's vote at the Royal Dublin Society hall, where Sinn Fein debated the April 10 accord.

The shift flies in the face of the Irish Republican Army's determination to see the British-ruled north unite with the rest of Ireland. The IRA-allied Sinn Fein now is free to help govern Northern Ireland along with other parties in a new 108-seat Belfast Assembly to be elected June 25.

Adams' victory may not increase overall public support for the May 22 referendums in Northern Ireland and the Irish Republic, which are required to ratify the accord. Indeed, Sinn Fein's belated embrace of the deal may fuel fears among the north's pro-British Protestants that it is contrary to their interests.

"Northern Ireland has been set adrift and pushed toward a united Ireland," said Peter Robinson, deputy leader of the Democratic Unionist Party, which is leading the "No" campaign for Protestants to reject an agreement.

Even a few months ago, the idea that Sinn Fein could approve a deal calling for a reformed Northern Ireland government seemed far-fetched.

But in this shifting political landscape, Sinn Fein is able to sell previously unpalatable compromise by pointing to how much pain it's causing Protestant opponents.

The Ulster Unionists, the major Protestant party, have suffered major defections to the "No" camp since accepting the deal last month.

The British and Irish governments combined to help Adams' sales pitch, too, highlighting the accord's promise to free several hundred IRA prisoners by mid-2000.

In an unprecedented gesture, both governments released four IRA prisoners for the day to speak at the conference. In particular, the surprise appearance of the IRA's longest-serving prisoners - four men convicted in 1975 of several bombings in England - sent the hall into thunderous applause.

David Trimble, leader of the Ulster Unionist Party and a supporter of the agreement, said Monday that Britain's Northern Ireland Secretary, Mo Mowlam, showed "considerable insensitivity" in allowing the prisoners to attend the meeting.

Mowlam defended the 36-hour prisoner releases as "a necessary step to take to convince people of the value and importance of the agreement . . . but I understand how difficult it is for people when they see it," she said in a BBC radio interview.

While the outcome was never in doubt, Sinn Fein and IRA leaders feared another ugly public split.

The modern "Provisional" IRA and Sinn Fein were born out of a bloody feud in 1969, and suffered another split in 1986 when Adams persuaded Sinn Fein to drop its boycott of the Irish parliament.

Republican Sinn Fein leader Ruairi O Bradaigh, whom Adams dethroned as Sinn Fein leader in 1983, said Sunday's vote demonstrated that his former party had "forsaken the revolutionary road to garner whatever fruits they can from their collaboration with British rule."